Various gunning compositions are known and used in the iron and steel industry for repairing and maintaining steel ladles, troughs, runners, spouts, electric furnaces, basic oxygen furnaces, and other equipment for containing and/or processing molten metal. Typically, these known gunning compositions are in a powdered form and include a major portion of a refractory base material (for example, calcined clay, mullite, brown fused alumina, tabular alumina); a minor portion of silicon carbide or graphite; further minor portions of ball clay, silicon carbide or graphite, and silicon metal; and a binder which advantageously includes colloidal silica. Examples of gunning compositions are provided in U.S. Pat. No. 5,147,834, issued to Banerjee.
An important aspect of a gunning composition is the ability to flow in the gunning process. In order to facilitate easy and uniform flow, conventional powdered gunning compositions have been mixed with water and sold in the form of damp mixtures. It is even more advantageous to pelletize the gunning compositions, when possible, into pellets having diameters of about 1-60 millimeters. However, it has been difficult to pelletize conventional gunning mixes due to their somewhat "sandy" or "pasty" nature prior to application.
An equally important aspect of a gunning composition is its ability to stick to an applied refractory surface, both during and after application. Therefore, when formulating the gunning compositions of the prior art, a significant challenge has been to develop compositions which would flow (and not self-agglomerate) prior to application, yet which would stick to applied surfaces, and resist erosion and corrosion, when exposed to molten iron or steel.